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Arthroscopic surgery is used to treat various conditions such as chondromalacia, or damaged articular cartilage, in joints, such as of the knee, shoulder, elbow, wrist, hip, and ankle. Articular cartilage is the tough, hyaline tissue covering the ends or articular surfaces of bones in the joints. Chondromalacia of cartilage is usually a result of diseased or traumatic induced changes in hyaline cartilage and may cause pain, stiffness, effusion, and/or grinding in the joint. A common treatment for chondromalacia involves the mechanical ablation or removal of the damaged or diseased tissue, such as with a rotary shaver. This procedure, however, may also remove healthy cartilage. Also, the rotary shaver tends to grab and tear tissue, leaving a rough surface that may slow healing and accelerate the onset of new chondromalacia.
Electrosurgical techniques have been proposed as alternatives to the mechanical ablation of tissue in arthroscopy, as well as for the coagulation of damaged and bleeding blood vessels encountered in arthroscopic surgical procedures. See, for example, U.S. Pat. Nos. 5,895,386 and 5,989,249, incorporated by reference herein. These patents disclose bipolar electrosurgical probes in which two coaxial electrodes are separated and covered by layers of an insulating material.
A problem with such prior art probes in arthroscopic surgery has been the breakdown of the insulation layers due to the high power and temperatures encountered during the use of electrosurgical instruments. Under high power, the tissue at the tip of an electrosurgical instrument may reach a temperature as high as 700xc2x0 C. to 900xc2x0 C. Although the temperature within the body of the probe is substantially less than 700xc2x0 C., the temperature is still sufficiently high that insulation formed from a conventional polyethylene would break down and render the electrosurgical instrument inoperative within a few seconds. Typically, electrosurgical ablators for arthroscopic surgery have used a polyvinylidene fluoride (PVDF), such as KYNAR(copyright), for the insulating layers. However, under high power, arcing at the tip of the electrodes may cause this insulating material to burn. Thus, in an arthroscopic procedure, the usable life of prior art electrosurgical instruments is limited by the insulating material. Also, the constant replacement of an inoperative instrument from the arthroscopic surgical site with a new instrument consumes both time and money and may also increase the risk of infection.
The present invention relates to a bipolar, fluid assisted coagulator/ablator probe that is capable of withstanding the high temperature, high power environment of arthroscopic surgery with an extended lifetime. The probe comprises an insulative housing and an elongated probe having a first longitudinal axis and extending from a proximal end retained within the insulative housing to a distal end extending from the insulative housing. The elongated probe further comprises a first tubular electrode forming a fluid conduit therethrough and having a first annular distal end face. A second tubular electrode is positioned concentrically around the first tubular electrode and has a second annular distal end face.
A first dielectric insulating layer is disposed between said first and second tubular electrodes, and a second dielectric insulating layer covers the second tubular electrode. The first and second dielectric insulating layers are a high temperature polyethylene capable of withstanding the high temperature, high power environment within the surgical site for at least two minutes before beginning to break down or burn.
A first bevel face is formed at the distal end of the probe, comprising the first and second annular distal end faces of the first and second electrodes, respectively. The bevel face is oriented obliquely with respect to the longitudinal axis of the probe and forms a first angle between the first bevel face and the longitudinal axis. The distal end of the elongated probe further comprises a first curve having a first radius of curvature. This configuration of the distal end is particularly suitable for use in the small arthroscopic surgery sites. The bevel face is also capable of a curette action by scraping.